Patent GB-641787-A (GB)
Title: Control systems and devices for dynamoelectric machines
Filed: 1946-10-04
Abstract: 641,787. Automatic control systems ; running generators in parallel. BENDIX AVIATION CORPORATION. Oct. 4; 1946. No. 29669. Convention date, Oct. 10, 1945. [Class 38 (iv)J In a system in which a predetermined division of load between a plurality of dynamo-electric generators supplying a common load is automatically maintained by interconnecting the electromagnets of electromagnetic regulators for the generators, each generator supplies current through a series resistance, the volt-drop across which energizes a relay controlling a contactor to disconnect the generator should its voltage fall below a predetermined value. Connection and disconnection of shunt wound D.C. generators 1, 1A, 1B, 1C to bus-bars 20, 21 supplying a load such as a battery 42 is controlled automatically and a predetermined load division between the connected generators maintained. Generator 1 is connected to the bus-bars by a relay 22 having an operating winding 24, the energization of which is controlled by a relay unit 15 containing two relays. The first relay has a winding 30 responsive to the voltage of generator 1 and closes a contact 40 at a predetermined generator voltage, which is below the bus-bar voltage, to energize a winding 38 of the second relay in accordance with the difference between the voltage of generator 1 and the bus-bar voltage. When the generator voltage exceeds the busbar voltage by a predetermined amount winding 38 assists a winding 31 responsive to generator voltage to close a contact 45 and thereby energize winding 24 to connect generator 1 to the bus-bars. The closing of relay 22 short circuits winding 38 but a winding 48 connected across interpole windings 4, of generator 1 is then energized, to assist windings 31, in accordance with the current supplied by the generator. Should the generator current reverse, winding 48, by opposing winding 31 ensures disconnection of the generator from the bus-bars. The re-introduction of winding 38 upon such disconnection ensures positive operation of the second relay. The voltage of the generator is at all times automatically controlled by a carbon pile regulator 13 having a pile 50, in series with the generator shunt field 3, controlled by a coil 60 responsive to generator voltage. Each generator has a similar relay unit and voltage regulator. Each regulator has a bias winding such as winding 65 adjusting the voltage setting to maintain automatically a predetermined division of load between the connected generators. These bias windings are connected between a common bus-bar 76, through contacts such as 70A of the first relay and a manual switch such as 74, and the slider of a potentiometer such as 79 across the interpole winding of the associated generator. Circulating currents in the bias windings due to variation in the relative voltages across interpole windings upon variation from the predetermined load division are in such a sense as to maintain the predetermined load division. The connection of each bias winding is controlled by the associated first relay. so that it is connected just prior to paralleling of a generator to cause an automatic rise of voltage of that generator. The interpole windings may have a positive temperature coefficient to reduce automatically, through the bias windings, the load on a generator which is overheating. Contacts 70A may be controlled by a separate relay responsive to generator voltage. Resistors may replace the interpole windings. Specification 608,508 is referred to.